Laser tipped catheter

Abstract

A laser catheter for insertion in a body passage and for treatment of a relatively inaccessible location with laser radiation in a preselected first wavelength range, typically in the mid-infrared band, that is outside the transmission passband of silica optical fibers. The laser catheter includes an elongated flexible tube, an optical fiber for carrying optical pumping laser radiation in a second wavelength range through the flexible tube, and a laser attached to the flexible tube at or near the distal end thereof and responsive to optical pumping laser radiation in the second wavelength range for generating output laser radiation in the first wavelength range. The laser can comprise a cylindrical laser crystal attached to the distal end of the flexible tube and having laser mirrors on opposite end faces thereof. The laser crystal can be a suitable host material doped with a rare earth ion selected to produce the desired output wavelength. A preferred laser crystal is erbium-doped YAG, which produces an output at 2.94 micrometers. The optical pumping radiation is supplied from an external pump laser, which is preferably an alexandrite laser operating in the wavelength range of 0.7 to 0.8 micrometer.

What is claimed is: 
     
       1. A laser catheter for internal application of laser radiation in a first wavelength range, comprising: an elongated, flexible element suitable for insertion in a body passage or cavity, said flexible element having a distal end and a proximal end;   optical waveguide means for carrying laser radiation in a second wavelength range through said flexible element; and   laser means attached to said flexible element at the distal end thereof and suitable for insertion in a body passage or cavity, said laser means being responsive to laser radiation in said second wavelength range carried by said optical waveguide means, for generating laser radiation in said first wavelength adjacent to an internal application site.   
     
     
       2. A laser catheter as defined in claim 1 wherein said optical waveguide means comprises a silica optical fiber having a prescribed passband for transmission of laser radiation without substantial attenuation and wherein said second wavelength range is within said prescribed passband. 
     
     
       3. A laser catheter as defined in claim 2 wherein said laser means comprises a laser crystal mounted to said flexible element, said laser crystal being capable of generating laser radiation in the mid-infrared band of wavelengths in response to optical pumping radiation in the 0.7 to 0.8 micrometer band of wavelengths. 
     
     
       4. A laser catheter as defined in claim 3 wherein said laser crystal comprises an erbium-doped host material selected from the group consisting of YAG, YLF and YSGG. 
     
     
       5. A laser catheter as defined in claim 3 wherein said laser crystal comprises a holmium-doped host material selected from the group consisting of YAG, YLF and YSGG. 
     
     
       6. A laser catheter as defined in claim 3 further including a laser source coupled to the proximal end of said optical fiber for generating laser radiation in said second wavelength range. 
     
     
       7. A laser catheter as defined in claim 6 wherein said laser source comprises an alexandrite laser. 
     
     
       8. A laser catheter as defined in claim 6 wherein said laser source comprises a laser diode. 
     
     
       9. A laser catheter as defined in claim 6 wherein said laser source is tunable over a range of wavelengths. 
     
     
       10. A laser catheter as defined in claim 2 wherein said first wavelength range is in the mid-infrared band of wavelengths. 
     
     
       11. A laser catheter as defined in claim 10 wherein said laser means comprises an annular laser crystal having inner and outer cylindrical surfaces with mirrors thereon, and said laser crystal further including means for redirecting laser radiation carried through said optical fiber to the inner cylindrical surface of said laser crystal, whereby said laser crystal provides laser radiation in said first wavelength range through said outer cylindrical surface. 
     
     
       12. A laser catheter as defined in claim 11 wherein said means for redirecting laser radiation comprises a reflecting surface within said annular laser crystal. 
     
     
       13. A laser catheter as defined in claim 12 wherein said reflecting surface has a conical shape. 
     
     
       14. A laser catheter as defined in claim 11 wherein said means for redirecting laser radiation comprises a section of said optical fiber within said annular laser crystal that is tapered to a smaller diameter than the remainder of said optical fiber. 
     
     
       15. A laser catheter as defined in claim 10 wherein said laser means comprises a cylindrical laser crystal having mirrors on opposite end faces thereof so as to produce a stable lasing cavity, said laser crystal being mounted to said flexible element so that laser radiation carried through said optical fiber is coupled through one end face of said laser crystal. 
     
     
       16. A laser catheter as defined in claim 15 wherein said laser crystal comprises a host material doped with a rare earth ion for providing laser radiation in a wavelength range between 1.0 and 3.5 micrometers. 
     
     
       17. A laser catheter as defined in claim 15 wherein said laser crystal includes a flat mirror on a proximal end face thereof and a curved mirror on a distal end face thereof. 
     
     
       18. A laser catheter as defined in claim 15 including matching means for efficiently coupling laser radiation in said second wavelength range to said laser crystal by substantially matching the radiation pattern from said optical fiber to a lasing region in said laser crystal. 
     
     
       19. A laser catheter as defined in claim 18 wherein said matching means comprises a section of said optical fiber near the distal end thereof adjacent to said laser crystal that is tapered to a larger diameter than the remainder of said optical fiber. 
     
     
       20. A laser catheter as defined in claim 1 wherein said second wavelength range is 0.7 to 0.8 micrometer and said first wavelength range is 1.0 to 3.5 micrometers. 
     
     
       21. A laser catheter as defined in claim 1 wherein said flexible element has a suitable size and flexibility for manipulation through a blood vessel. 
     
     
       22. A laser catheter as defined in claim 1 wherein said optical waveguide means has a prescribed passband for transmission of laser radiation without substantial attenuation and wherein said second wavelength range is within said prescribed passband. 
     
     
       23. Apparatus for internal treatment with radiation in a selected first wavelength range, comprising: an elongated, flexible tube for insertion in a body passage or cavity, said tube having a distal end and a proximal end;   optical waveguide means for carrying laser radiation in a second wavelength range through said tube; and   means for generating radiation in said first wavelength range adjacent to an internal treatment site, said generating means being affixed to said tube at the distal end thereof and being responsive to radiation in said second wavelength range carried through said optical waveguide means.   
     
     
       24. Apparatus as defined in claim 23 wherein said optical waveguide means comprises a silica optical fiber. 
     
     
       25. Apparatus as defined in claim 24 wherein said generating means comprises a laser and wherein radiation in said second wavelength range is coupled from said optical fiber to said laser for optical pumping thereof. 
     
     
       26. Apparatus as defined in claim 25 wherein said first wavelength range s in the mid-infrared band. 
     
     
       27. Apparatus as defined in claim 25 wherein said laser comprises a cylindrical laser crystal having mirrors on opposite end faces thereof, said laser crystal being mounted to said tube so that laser radiation carried through said optical fiber is coupled to one end face of said laser crystal. 
     
     
       28. Apparatus as defined in claim 25 wherein said laser comprises an annular laser crystal having inner and outer cylindrical surfaces with mirrors thereon, and further including means for redirecting laser radiation carried through said optical fiber to the inner cylindrical surface of said laser crystal, whereby said laser crystal provides laser radiation in said first wavelength range through said outer cylindrical surface. 
     
     
       29. Apparatus as defined in claim 24 wherein said generating means comprises a nonlinear crystal selected to convert radiation in said second wavelength range to radiation in said first wavelength range. 
     
     
       30. Apparatus as defined in claim 29 wherein said nonlinear crystal comprises lithium niobate responsive to laser radiation at wavelengths of 0.85 micrometer and 1.06 micrometers for generating radiation at 4.26 micrometers. 
     
     
       31. Apparatus as defined in claim 29 wherein said nonlinear crystal comprises lithium niobate. 
     
     
       32. A method for treatment of a selected internal body location with radiation in a selected first wavelength range, comprising the steps of: advancing a catheter containing an optical waveguide through a body passage or cavity to the vicinity of the selected location;   transmitting radiation in a second wavelength range through said optical waveguide to the vicinity of the selected location; and   generating radiation in said first wavelength range for treatment of the selected location, said generating step being carried out in the vicinity of the selected location in response to radiation in said second wavelength range transmitted through said optical waveguide.   
     
     
       33. A treatment method as defined in claim 32 wherein the step of transmitting radiation in a second wavelength range includes the step of transmitting radiation through a silica optical fiber. 
     
     
       34. A treatment method as defined in claim 33 wherein the step of generating radiation in said first wavelength range includes the step of generating laser radiation with a laser attached to said catheter at or near the distal end thereof. 
     
     
       35. A treatment method as defined in claim 34 wherein the step of generating laser radiation includes the step of generating laser radiation in the mid-infrared band of wavelengths. 
     
     
       36. A treatment method as defined in claim 34 wherein the step of generating laser radiation includes the steps of providing a generally cylindrical laser crystal having laser mirrors on opposite end faces thereof, and   coupling radiation in said second wavelength range from said optical fiber through one end face of said laser crystal for optical pumping thereof.   
     
     
       37. A treatment method as defined in claim 34 wherein the step of generating laser radiation includes the steps of providing an annular laser crystal having inner and outer cylindrical surfaces with laser mirrors thereon, and   redirecting laser radiation in said second wavelength range from said optical fiber to the inner cylindrical surface of said annular laser crystal for optical pumping thereof.   
     
     
       38. A catheter assembly for internal treatment with radiation in a first wavelength range, comprising: an elongated, flexible catheter adapted for insertion in a body passage or cavity, said catheter having a distal end and a proximal end;   optical waveguide means for carrying radiation in a second wavelength range through said catheter; and   means attached to said catheter at the distal end thereof and responsive to radiation in said second wavelength range for generating radiation in said first wavelength range adjacent to an internal treatment site.   
     
     
       39. A catheter assembly as defined in claim 38 wherein said means for generating radiation comprises laser means. 
     
     
       40. A catheter assembly as defined in claim 39 wherein said optical waveguide means comprises an optical fiber having a prescribed passband for transmission of radiation and wherein said second wavelength range is within said prescribed passband. 
     
     
       41. A catheter assembly as defined in claim 40 wherein said catheter comprises an elongated, flexible tube. 
     
     
       42. A catheter assembly as defined in claim 41 wherein said laser means comprises a laser crystal having mirrors on opposite end faces thereof so as to produce a stable lasing cavity, said laser crystal being mounted to said flexible tube so that radiation carried through said optical fiber is coupled through one end face of said laser crystal. 
     
     
       43. A catheter assembly as defined in claim 42 wherein said laser crystal comprises a host material doped with a rare earth ion for providing laser radiation in a wavelength range between 1.0 and 3.5 micrometers. 
     
     
       44. A catheter assembly as defined in claim 38 wherein said first wavelength range is in the mid-infrared band of wavelengths. 
     
     
       45. A catheter assembly as defined in claim 38 wherein said means for generating radiation comprises a nonlinear crystal.